Triarylmethane dyes are synthetic

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s containing

triphenylmethane Triphenylmethane or triphenyl methane (sometimes also known as Tritan), is the hydrocarbon with the formula (C6H5)3CH. This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is the basic skeleton of many syn ...

backbones. As

dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...

s, these compounds are intensely colored. They are produced industrially as dyes.

Families

Triarylmethane dyes can be grouped into families according to the nature of the substituents on the aryl groups. In some cases, the

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s associated with the cationic dyes (say crystal violet) vary even though the name of the dye does not. Often it is shown as chloride.

Methyl violet dyes

Methyl violet dyes have dimethylamino groups at the ''p''-positions of two aryl groups. Image:Methyl Violet 2B.svg, Methyl violet 2B Image:Methyl Violet 6B.svg, Methyl violet 6B Image:Kristallviolett.svg, Methyl violet 10B

Fuchsine dyes

Fuchsine dyes have primary or secondary amines (NH₂ or NHMe) functional groups at the ''p''-positions of each aryl group. File:Pararosaniline.png,

Pararosaniline Pararosaniline, pararosaniline free base, Basic Red 9, or C.I. 42500 is an organic compound with the formula . It is the free base form of pararosaniline hydrochloride, , a magenta solid with a variety of uses as a dye. It is one of the four comp ...

File:Rosaniline hydrochloride.svg,

Fuchsine Fuchsine (sometimes spelled fuchsin) or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl.

(hydrochloride salt) Neofuchsin.svg,

New fuchsine New fuchsine is an organic compound with the formula H2N(CH3)C6H3)3Cl. It is a green-colored solid that is used as a dye of the triarylmethane class. It is one of the four components of basic fuchsine, and one of the two that are available as ...

(As chloride) Fuchsine acid vector.svg, Fuchsine acid

Phenol dyes

Phenol dyes have hydroxyl groups at the ''p'' positions of at least two aryl groups. File:Phenolphthalein-low-pH-2D-skeletal.svg,

Phenolphthalein Phenolphthalein ( ) is a chemical compound with the chemical formula, formula carbon, C20hydrogen, H14oxygen, O4 and is often written as "HIn", "HPh", "phph" or simply "Ph" in shorthand notation. Phenolphthalein is often used as an indicator in ...

File:Phenol-red-zwitterionic-form-2D-skeletal.png,

Phenol red Phenol red (also known as phenolsulfonphthalein or PSP) is a pH indicator frequently used in cell biology laboratories. Chemical structure and properties Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per ...

File:Chlorophenol red.png, Chlorophenol red File:Cresol Red.svg, Cresol red File:Bromocresol purple.svg,

Bromocresol purple Bromocresol purple (BCP) or 5′,5″-dibromo-''o''-cresolsulfophthalein, is a dye of the triphenylmethane family (triarylmethane dyes) and a pH indicator. It is colored yellow below pH 5.2, and violet above pH 6.8. In its cyclic sulfonate ester f ...

File:Bromocresol green.svg,

Bromocresol green Bromocresol green (BCG) is a dye of the triphenylmethane family ( triarylmethane dyes). It belongs to a class of dyes called sulfonephthaleins. It is used as a pH indicator in applications such as growth mediums for microorganisms and titrations ...

Malachite green dyes

Malachite green dyes are related to the methyl violet dyes, except that they contain one phenyl (C₆H₅) group. Image:Malachite green structure.svg ,

Malachite green Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is ...

Image:Structure of the dye brilliant green.png, Brilliant green (dye) Image:Brilliant Blue FCF(2).svg, Brilliant blue FCF, a common food colorant

Victoria blue dyes

Victoria blue dyes are related to the methyl violet dyes, except they contain one naphthylamino group. Variation is found is dimethylamine vs diethylamino substituents on the phenyl rings and variations of the secondary amine on the naphthyl group. File:Victoria blue B with charge.svg, Victoria blue B File:Victoria blue FBR revised.svg , Victoria blue FBR File:Victoria blue BO.svg, Victoria blue BO File:Victoria pure blue FGA revised.svg, Victoria blue FGA File:Victoria blue 4 R revised.svg, Victoria blue 4 R File:Victoria blue R revised.svg, Victoria blue R

Xanthene dyes

Xanthene dyes feature a

xanthene Xanthene (9''H''-xanthene, 10''H''-9-oxaanthracene) is the organic compound with the formula CH2 6H4sub>2O. It is a yellow solid that is soluble in common organic solvents. Xanthene itself is an obscure compound, but many of its derivatives are u ...

core. They are not widely used as textiles, but for other applications. File:EosinB.png, Eosin B File:EosinY.png,

Eosin Y Eosin Y, also called C.I. 45380 or C.I. Acid Red 87, is a member of the triarylmethane dyes. It is produced from fluorescein by bromination. Use Eosin Y is commonly used as the red dye in red inks. It is commonly used in histology, most nota ...

File:rhodamine B.svg, Rhodamine B File:Rhodamine 123.svg, Rhodamine 123 File:Fluorescein 2.svg ,

Fluorescein Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to Triarylmethane dye, triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. ...

Bridged arenes

Where two of the aryl groups are bridged by a

heteroatom In chemistry, a heteroatom () is, strictly, any atom that is not carbon or hydrogen. Organic chemistry In practice, the term is mainly used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular ...

, these triarylmethane compounds may be further categorized into

acridine Acridine is an organic compound and a nitrogen heterocycle with the formula C13H9N. Acridines are substituted derivatives of the parent ring. It is a planar molecule that is structurally related to anthracene with one of the central CH groups ...

s (nitrogen-bridged),

s (oxygen-bridged), and

thioxanthene Thioxanthene is a chemical compound in which the oxygen atom in xanthene is replaced with a sulfur atom. It is also related to phenothiazine. Several of its chemical derivative, derivatives are used as typical antipsychotics in the treatment of sc ...

s (sulfur-bridged).

Synthesis

The amine-containing dyes are often prepared from Michler's ketone or its diethylamino analogue. In this way, the third aryl group is readily differentiated. The Friedel–Crafts alkylation reaction is a popular method to prepare many of the phenolic derivatives: : ThymolphthaleinSynthesis

Applications

In addition to their dominant use as dyes, many of these dyes react reversibly with acid and base, and thus serve as

pH indicator A pH indicator is a halochromism, halochromic chemical compound added in small amounts to a Solution (chemistry), solution so the pH (acidity or Base (chemistry), basicity) of the solution can be determined visually or spectroscopically by chang ...

s. :

References

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